Nuclear doesn't scale quickly. It already adapts from 4GW to 7GW in Spain, but it does it slowly and ahead of weather conditions.
What is needed is more co-located battery storage, and more gravity (solid or water) storage.
Nuclear is never meant to scale, you want to run the plant at 100% as much as possible to recoup costs. It is baseload power and you deal with peaks using peaker plants and batteries.
Maybe I don’t understand the requirement, but can’t a constant-rate supply provide stored power for peak demand and support baseline consumption off-peak?
Nuclear is different to fossil fuel power. It comes from a renewable source. It is bad only because it produced waste, but we're working towards solving this issue.
Uranium is not a renewable resource. All of the uranium on earth was formed in another star’s supernova and seeded in the proto planetary nebula before the earth coalesced.
That's why you use a fast neutron (breeder) reactor to extract up to 90% of the potential fissionable "fuel" from that uranium instead of just a few percent. Another option is the use of thorium of which is there is ca. 3 times as much. By the time both uranium and thorium run out there'll either be practical fusion energy or one of those new battery technologies which are always popping up.
Now we just have to invest a few hundred billion for a few decades until er have practical commercial breeder reactors, while still burning coal and gas while we wait and see whether the engineers can figure it out.
That's it. If you need to have nuclear capacity for a grid for say 30GW, despite average usage being just 10GW, your price is now $300/MWh rather than $100/MWh if you can run them 24/7
Why? All modern nuclear reactors do load following. I believe it’s even an EU requirement. And certainly the practice in France.
Nuclear costs the same thing whether you use it or not. If you meet the peak energy demand with nuclear you might as well save the construction of intermittent renewables.